A General Class of Commutative Filters for LES in Complex Geometries

Vasilyev, Oleg V.; Lund, Thomas S.; Moin, Parviz

doi:10.1006/jcph.1998.6060

Cited by 345 publications

(241 citation statements)

References 9 publications

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“…It is assumed here that the commutation between the spatial filter and the derivative is satisfied, as in single-phase LES modeling [20,53]. This assumption is reasonable as the commutation error depends more on the topology of the mesh than on the characteristic of the flow [54,55].…”

Section: Parametermentioning

confidence: 99%

A priori filtering and LES modeling of turbulent two-phase flows application to phase separation

et al. 2018

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The Large Eddy Simulation (LES) of two-phase flows with resolved scale interfaces is investigated through the a priori filtering of Direct Numerical Simulations (DNS) of one-fluid and multifield models. A phase inversion benchmark [1][2][3][4] is considered highlighting many coalescence and interface rupture events in a kind of atomization process. The order of magnitude of specific two-phase subgrid LES terms is first considered with the two modeling approaches. Then, different existing models such as Smagorinsky [5], Wall-Adapting Local Eddyviscosity (WALE) model [6], Bardina [7], Mixed [8] and Approximate Deconvolution Model (ADM) [9] are used to account for two-phase subgrid effects. These models are compared to filtered DNS results. The main conclusion concerning a priori LES filtering is that the inertia term is not predominant in two-phase flows with fragmentation and rupture of interface. This conclusion is different from that of the studies of [3,[10][11][12][13]. concerning LES models, functional modeling do 1 not correlate to filtered DNS results whereas structural approaches do. Bardina and ADM are clearly the good LES framework to consider for two-phase flows with resolved scale interfaces. ADM is clearly better than Bardina in our study. The authors greatly acknowledge the reviewer for its comments and remarks that have guided us in improving the technical and editorial aspects of the manuscript. From a general point of view, all the comments and remarks recommended by the reviewer have been taken into account. They are highlighted in the text in red. More specifically, we can detail them as follows: COMPUTERS & FLUIDS 1) I would recommend to add the main conclusions to the abstract and to add a separate section conclusions to the paper.In agreement with reviewer remark and in order to improve the fast reading and understanding of the paper, we have included a conclusion part in the abstract. In addition, the last section have been extended to "Summary, conclusion and future work", with addition of conclusions in order to highlight the originality and main results of the work. 2) Abstract : DNS and ADM should be defined.Done. The same has been achieved for the Wall-Adapting Local Eddy-viscosity (WALE) model. 3) A streak of the interface points towards the upper left corner of the box. Is that physical?Yes, this a physical feature of the interface. As we are dealing with liquid-liquid twophase flows, when the light fluid (blue surface) goes to the top part of the cavity under gravity effects, heavy liquid can be trapped near vertical walls or vertical corners, inducing this king of interface topology.4) The sentence "Among the few existing …" seems to have a grammar mistake. Detailed Response to ReviewersThis sentence has been rewritten as follows "Among the few existing references, it is worth mentioning the work on LES formulation for the one-fluid model and subsequent a priori LES filtering of DNS simulations for the estimate of new specific two-phase contributions in the mass, momentu...

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Section: Parametermentioning

confidence: 99%

A priori filtering and LES modeling of turbulent two-phase flows application to phase separation

et al. 2018

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“…The top-hat filter in ͑3͒ is called symmetric if a =−b Ͻ 0, but this definition also allows for general asymmetric or "skewed" filters 23,24 for which x is not the central point of the integration interval. We will show in Sec.…”

Section: Decomposition Of the Numerical Turbulent Stress Tensormentioning

confidence: 99%

“…We notice that the filter corresponding to a higher-order spatial discretization is itself a higher-order filter; with increasing order, the Fourier transform of the kernel is seen to stay closer to the identity operator for a wider range of wave numbers. 21,22,24 Each discretization method gives rise to a particular damping of the amplitude of individual modes, which induces a specific dynamic contribution in an actual large-eddy simulation based on this method. The role of the total filter is discussed further in, e.g., Refs.…”

Section: -6 B J Geurts and F Van Der Bosmentioning

confidence: 99%

“…18 In case an upwind discretization method is adopted, the induced filter is skewed and contributes to both dispersive and dissipative aspects of the smaller resolved scales. 23,24 To quantify the induced filter of upwind methods in more detail, we first require the effect of a skewed top-hat filter on a Fourier mode e ıKx . This is readily obtained as…”

Section: ͑32͒mentioning

confidence: 99%

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Numerically induced high-pass dynamics in large-eddy simulation

Geurts¹,

Bos²

2005

Physics of Fluids

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The numerical distortion of the smallest resolved-scale dynamics in large-eddy simulation may be understood in terms of the filter that is induced by the spatial discretization. At marginal subfilter resolution r = ⌬ / h, with filter width ⌬ and grid spacing h, the character of the large-eddy closure problem is strongly influenced by the numerical method. We show that additional high-pass contributions arise from the spatial discretization. The relative importance of, on the one hand, the turbulent stresses and, on the other hand, the numerically induced contributions, is quantified for general finite differencing methods. We derive and analyze the induced filters for several popular discretization methods, including higher order central and upwind methods. The application of these induced filters to small-scale turbulent flow structures gives rise to a characteristic amplitude reduction and phase shift. Their dynamic relevance is quantified in terms of the subfilter resolution. The numerical high-pass effects are found to be negligible if the subfilter resolution is large enough ͑r տ 4͒. Conversely, the numerically induced effects are comparable to, or even larger than the turbulent stresses as r =1-2.

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“…The momentum advection and scalar advection that were solved by the fourth order central and the third order positive method [14], respectively. The nonlinear terms are filtered with filter width equal to two cell widths [15]. The sigma subgrid model [16] is utilised in subfilter (subgrid) scales computations.…”

Section: Numerical Modelmentioning

confidence: 99%

Ventilation of idealised urban area, LES and wind tunnel experiment

Kukačka

Fuka

Nosek

et al. 2014

EPJ Web of Conferences

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Abstract. In order to estimate the ventilation of vehicle pollution within street canyons, a wind tunnel experiment and a large eddy simulation (LES) was performed. A model of an idealised urban area with apartment houses arranged to courtyards was designed according to common Central European cities. In the wind tunnel, we assembled a set-up for simultaneous measurement of vertical velocity and tracer gas concentration. Due to the vehicle traffic emissions modelling, a new line source of tracer gas was designed and built into the model. As a computational model, the LES model solving the incompressible Navier-Stokes equations was used. In this paper, we focused on the street canyon with the line source situated perpendicular to an approach flow. Vertical and longitudinal velocity components of the flow with the pollutant concentration were obtained from two horizontal grids placed in different heights above the street canyon. Vertical advective and turbulent pollution fluxes were computed from the measured data as ventilation characteristics. Wind tunnel and LES data were qualitatively compared. A domination of advective pollution transport within the street canyon was determined. However, the turbulent transport with an opposite direction to the advective played a significant role within and above the street canyon.

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A General Class of Commutative Filters for LES in Complex Geometries

Cited by 345 publications

References 9 publications

A priori filtering and LES modeling of turbulent two-phase flows application to phase separation

A priori filtering and LES modeling of turbulent two-phase flows application to phase separation

Numerically induced high-pass dynamics in large-eddy simulation

Ventilation of idealised urban area, LES and wind tunnel experiment

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